Telecommunication switching system



Nov. 30, 1948. ca. DEAKIN TELECOMMUNICATION SWITCHING SYSTEM Filed Aug; 28, 1943 5 Sheets-Sheet 1 INVENTOR GERALD Dffll /N ATTORNEY 9 Nov. 30, 1948.

Filed Aug. 28, 1943 G. DEAKlN TELECOMMUNICATION SWITCHING SYSTEM 6V is E 'Q FF l til 2% 3 Sheets-Sheet 2 i i am INVENTOR GERALD DEA/ IN a I BY ATTORNEY 2 G. DEAKIN TELECOMMUNICATION SWITCHING SYSTEM Nov. so, 1948.

3 Sheets-Sheet 3 Filed Aug. 28, 1943 Patented Nov. 30, 1948 2,454,780 TELECOMMUNSISATION SWITCHING Gerald Deakln, ternaiional TEM New York, N. Y., minor to In- Standard Electric Corporation,

New York, N. Y., a corporation of Delaware Application August 28, 1943, Serial No. 500,412

This invention relates to new and useful improvements in controlling systems of the type adapted for use in controlling the numerical setting of switches, e. g. like the ones used in automatic telephone exchange systems.

The present invention may be used in combination with some of the circuits and devices disclosed in my co-pending application, Serial No. 484,184, filed April 23, 1943, now Patent 2,354,682 granted Aug. 1, 1944, the co-pending application of Henry F. Herbig, Serial No. 485,827, filed May 6, 1943, now Patent 2,380,950 granted Aug. '1, 1945, and the applications referred to therein.

In switch controlling systems of the type described in said applications, two numerically operable switches, e. g. an automatic telephone exchange selector switch and a register controller, are so connected that the selector will be numer ically set in accordance with the numerical setting of the register controller. The numerical setting of the register is usually determined by a comparatively complex and slowly operating device, e. g. the customary sub-station calling dial. The dial must be successively operated lor each digit and the operator must wait for its return to normal before he can re-operate the dial for the next digit.

In order to speed up operation, various types of keyboards, or key-controlled senders, have been used, particularly at central exchange operators positions. Whereas dials control the switches over a two-wire circuit, the faster keycontrolled senders require a larger number of control wires, or are mechanically more complicated than the dial senders. For these reasons their provision at subscribers stations, or at P. B. X operators positions, was generally considered as too expensive to be practicable.

According to the present invention, the control circuit of one of the selectively operable switches, e. g. the register in case of an automatic telephone system, is so arranged as to permit the use of a simple contact device as a controller for variably operating the register.

The simple contact device may take the form of a row of, say ten keys, the setting of which is recorded on or stored in the register as fast as the keys are actuated. Only the customary twowire connection is needed between the controller and the register, the latter being adjusted to record the setting of the keys as fast as the keys can be actuated.

Some of the features of this invention may be adapted for use with a dial type of digit transmitting means instead of keys.

An embodiment 3 Claims. (Cl. 177-353) of such an arrangement is described hereinafter in which the successive potentials controlling the register do not originate from a device located at the calling station and employing keys and a 5 voltage divider. Instead they are provided by an impulse operated automatic switch which is located in the calling ofli'ce, which is adapted to select voltages from a source provided in the calling oflice, and which makes the selection under the control of conventional'impulse dialing at the subscriber station.

In this case the controller may be arranged as a simple step-by-step switch which, in its various positions, actuates a different contact for determining the setting of a register or the like.

These and other features of the invention will be set forth in greater detail in the following description and the appended claims.

The drawings illustrate diagrammatically three embodiments of the invention;

Figs. 1 and 2, placed one above the other, represent as much of a P. B. X telephone system as is necessary for understanding the present invention;

Fig. 1(a) is a modification of the subscriber's station shown in Fig. 1, and

Fig. 3, when placed above'Fig. 2, illustrates the manner in which the invention could be applied for controlling connections through two central telephone exchanges.

Referring to Fig. 1, each subscribers station is provided with the usual telephone set I and, if the subscriber is entitled to outside service, also an impulse dial indicated at 2. For controlling the establishment of local calls, the station is provided with a single row of ten push buttons numbered 1-0 (only 1 and 2 are shown) adapted when actuated to insert sections 3 of a potentiometer in a connection to a 20-volt 40 battery.

Upon the initiation if station I, the station is onnected by means such as a line finder or the like, to a P. B. X switchboard and over wires 6, 1 and 8 and suitable switches (not shown) with a register controller illustrated in Fig. 2.

The P. B. X switchboard includes a final selector and, if required, one or more group selectors also. The register controller comprises, in

addition to what is disclosed in my prior application, ten sets of muiti-electrode discharge devices variably operable in accordance with the key depressed at the calling station. The register includes also several sets of four digit storing relays XRI, 2, 3 and 4, one set for each digit.

a call at the calling Thus, a system requiring switch control by three digits would have twelve such XR relays and a seven digit system of twenty-eight XR relays. For the sake of simplicity, only one set is illustrated in the drawing and the connections to the other sets are merely indicated. When energized singly or in combination, each set of XR. relays effects a connection of a selected one of ten different D. C. potentials to a terminal, such as the one in Fig. 2, which is designated as O, of an "out control" switch E of the register. Each further set of XR relays causes a connection of another selected D. C. potential to another terminal in the same bank of the switch E0. The number of such connections depends on the number of digits required by the control system. As shown in Fig. 2 there is an inner row of terminals multipled together and a wiper A of the terminals in the outer bank such as 0, I, 2 to the terminal in has a corresponding position. In this way, since the inner row performs a function corresponding to that of a slip ring, a connection may be made from any part of this row (for example, from the part indicated in the drawing by an arrow head) to voltage comparing apparatus, not shown, which according to known art, is adapted to stop the hunting of a selector switch when it finds among its testing terminals a potential equal to that provided from an outer row terminal of switch E0. In operation, one selector is controlled in this way while the wiper of switch E0 is positioned so that it selects one of the potentials stored on its outer row of terminals. Then, after the flrst selector has stopped in the intended position another selector is switched into the voltage comparing circuit and the wiper of switch E0 is moved over to another terminal by means which are well known and are no part of this invention, and thus the register is prepared to control the next selector by the use of another stored potential.

A complete register is disclosed in my said copending application and particularly in Figs. 10, a, 10b and 18 thereof. The fundamental circuit used in the system disclosed in my said application, includes two brushes (A and B) of each register switch, whereas the fundamental circuit used in the present system requires only one register bnish A. switches are the same.

When the line is extended to the P. B. X switchboard, a circuit is closed from grounded battery over the left-hand winding of relay DR, left hand inner armature and back contact of relay HR, line B, the subscribers telephone set I, contacts 24, line A, and the right-hand winding of relay DR to ground. This relay becomes energized and locks up over its left-hand front contact and armature and closes an energizing circuit from ground over its right-hand outer armature and front contact, back contact and armature 4 of relay CR and winding of relay HR to grounded battery, and in parallel over armature 5 of CR, conductor 1 and the winding of relay MR to grounded battery.

Relay HR opens the TR2, etc. One TR group of XR relays.

The calling subscriber depresses keys in accordance with the designation of the called line. When any of the keys 1 to 0 is depressed, a flat adapted to connect any the inner row which Otherwise, the register pressed, 9. negative plunger I 2 attached thereto moves down with it. Rectangular slots in the frame In guide the plunger. A cam surface l2a formed on the plunger l2 engages a roller l5 mounted on a rod ll, slidably mounted in slots of the frame Hi. The rod It will thus be moved to the left. A pawl 20 is pivoted on rod H at 2| and is held in the position shown by means of a coiled spring 22. The head 20a of the pawl engages a finger I811 01' a bar i8, slidably mounted in brackets I 9 on the frame l0. When, therefore, the rod H is moved to the left it will, through the agency of pawl 20, move the bar I 8 also to the left against the tension of spring i8b. When this happens, contact 24, which is mounted on but insulated from rod i8, is moved away from contact 25, which is mounted on but insulated from the frame I 0.

When the plunger is about half-way down, the contact 24 will be moved far enough to engage a contact 28, which is mounted on the frame I0.

When the plunger I2 is about flve-eighths of the way down, an insulator l3 attached thereto, engages spring i8 and forces it into contact with spring l1, both springs being mounted but insulated from the frame Hi.

When the plunger i2 is all the way down, the roller l5 will have moved the rod I 4 far enough to the left for the heel 20b of the pawl to come in contact with the frame I p. This will rotate the pawl 20 around its pivot 2i against the tension of spring 22 and release the rod l8. The rod I8 is returned to normal under the tension of spring l8b, opening contact 26 and closing contact 25.

When the button is released, it is returned to normal under the action of spring II and the slide I4 is returned to normal under the action of spring 23. The finger I8a will now again be engaged by the pawl. The contact between l6 and i1 opens when the plunger is three-eighths of the way to its normal position.

When contacts 24, 25 open, the calling line circuit is opened and relay DR become deenergized.

When l6 and I! make contact, a circuit is momentarily closed from ground over the righthand armature and front contact of relay HR (which is slow acting and does not fall 011 immediately upon the de-energization of DR), the right-hand inner back contact and armature of DR, the A wire, and contacts 24, 26, to one end of the potentiometer. Depending on the key depressed, 20-volt grounded battery is connected over a certain number of potentiometer sections 3, the depressed key contacts l6, l7, wire B, lefthand armature and back contact of DR, lefthand outer armature and front contact of HR to conductor 6. Thus, depending on the key depressed, a D. C. potential of a value between -2 and 20 volts is momentarily applied to the B wire. Assuming that the number 5 key was depotential of 10 volts is applied.

connected to the tubes and the cathods of V2.

The grid of each V2 tube and the tube, is conapplied over tube is con- The gas valve GV of the accuse The arrangement of any pair of triodes is such that their combined plate resistances are connected in shunt across'the control gap or the gas tube with which they are associated. A positive potential is applied across the control gap, as wel as to these tubes which are in parallel to it, from HTB via dropping resistor R3. At times where a gas valve is non-conductive the potential applied to its control electrode will be of some value less than the full high tension supply level depending on the voltage drop across R3 which, of course, is governed by the effective combined plate impedance of the triodes. Ifeither or both of the triodes should pass a large current, the drop across R3 will be relatively large and the control electrode will be far below the potential at which it is adapted to cause the gas valve to ignite. If the triodes combined plate resistance is progressively increased, i. e. if the combined plate current is made smaller and smaller, the drop across R3 will diminish progressively and the voltage applied to the control electrode will rise toward the level of HTB until its attains a value which will cause the gas valve to fire. The triodes VI, V2, the resistor R3, and the level of HTB potential are selected so that the combined currents through both triodes when neither has any appreciable grid bias will be significantly less than the combined current under any of a plurality of other conditions of bias value combinations wherein one of the tubes may be completely out off and draw no current because of a substantial negative grid bias, but the other draws relatively heavy current (or is even saturated) because its grid bias is substantially positive. It is obvious that where the cathode of one triode in each pair and grid of the other are connected to the same negative source of potential, that where, thereupon, a succession of different values of negative potential are applied, respectively, to the control rid of the one and the cathode of the other, and that. where the magnitude of the differences between the succession of different potentials is substantial, the invariable effect will be to cut off one tube entirely but to do the exact converse to the other (thus causing it to pass a large current) in every case except one in which the potential supplied from the two separate sources are of the same magnitude. In that case, while neither tube will be completely cut oif, at the same time it will not pass much current and the combined current will be much less than in any other case.

As is well known, the gas valve is a device which, once its gas content is ionized, will start to draw current heavily and will continue to do so even if the original ionizing position is eliminated. Once it fires its control electrode loses control. Therefore, should the condition of the triodes be appropriate to cause ionization, then, even if this condition be of extremely short duration, the gas valve will positively respond and it will continue to draw a very heavy current whatever happens to the control electrode unless its anode potential is removed or very considerably reduced.

The subscriber must press the key all the way down without hesitation, but he may hold it down as long as he wishes. Whether he releases the key immediately or holds it down, the line circuit will be closed over the contacts 24, 25, and when relay HR falls away and makes its back contact, the relay DR again becomes energized and remains energized until the next key is depressed.

Since the number 5 key was actuated at the calling station and the relay GVRI, 2, was energized by the GVof V05, the relays XRI and XR2 will be energized over circuits including the back contacts of TR! and the front contacts of GVRI, 2. An energizing circuit is also closed for relay ZGVR. The relays KB! and 2 lock up in multiple over the winding of TRI to the ground and front contact of MR. TRI transfers the valve circuit to the back contacts of the next transfer relay TR2 over which a second group of storing relays may be operated. 2GVR opens the high tension battery connection to the valve circuits and thus de-ionizes the gas valve of VC5 and causes the de-energization of relay GVRI, 2.

Depending on the energization of one or more relays XRl--4, one of ten different D. C. potentials of 2-20 volts is connected over the contacts of these relays to the terminals of the' E0 switch. As partially shown, bank A of the switch E0 is connected as follows, on the operation of the XR relays:

'-2 volts when XRI is operated,

4 volts when XR2 is operated.

6 volts when XR3 is operated,

-8 volts when XR4 is operated,

-10 volts when XRI and 2 are operated,

-l2 volts when XRI, 2 and 3 are operated, -l4 volts when XRI, 2, 3 and 4 are operated, 16 volts when XRI, 2 and 4 are operated, 18 volts when XRI and 3 are operated, and --20 volts when XRI and 4 are operated.

There is one group of digit storing relays XR for each digit of the called subscribers number, but the ten valve circuits are common to all the digit storing relays. One transfer relay TR is provided for each digit group except the last, as above stated, and the function of these relays is to transfer the valve circuit to the next digit storing group when the preceding digit has been recorded.

The XRI and XR2 relays, in the XR relay group of digit 1, are left in their holding conditions. Therefore, they store the negative potential which they selected bya fixed connection to the 0 terminal of the outer bank of the E0 switch.

When the keying is complete, the register circult is automatically disconnected from the P. B. X switchboard, e. g. in the manner disclosed in my said co-pending application. As here indicated, this is accomplished by the application of ground over all the energized TR relays to conductor 8 and thence over. a back contact, armature 3 and winding to relay CR to grounded battery. This relay becomes energized and locks up to ground over the right-hand front contact and armature of DR. The relay CR causes the deenergization of HR and the disconnection of the register.

The D. C. potentials applied to the terminals of the register switch E0 by the XR relays will control the numerical operation of the necessary number of selectors including the final selector in the manner disclosed in the applications above mentioned.

If preferred. a small rectifier may be provided at the P. B. X board, or at the sub-station, in

lieu of the connection to the central exchange battery shown in Fig. 1. This is illustrated in Fig. 1a. The alternating current mains are inductively connected over a transformer TT and a full wave rectifier S to one end of the potentiometer 3. over a resistance R2 and to the other end over a resistance R3 and a contact 30 which is closed while any of the keys is depressed.

line loop,

-including a back contact of must be identical, and the voltages at the potentiometer 3 and the register must be closely controlled. Since very little power is involved, the

battery-at the central ofllce may be of the smallest commercial type and floated on a controlled voltage rectifier S at the P. B. X. The voltage of the rectifier may be controlled by means of a stabilizing gas valve VS bridged across. the rectifier circuit. Thistype of valve will maintain the D. C. voltage within a small fraction of 1% when the load is more or less constant. At constant D. C. load the voltage of the As C. power supply may be maintained constant within a 10.1% for :10% variation in the A. C. supply.

The single pulse sending arrangement above disclosed could be used also to good advantage for controlling multi-ofiice connections. This is illustrated in Fig. 3. The calling station I by closing the line circuit will be connected over suitable means such as line finder and selector switches to one end of a two-wire inter-office trunk and therethrough to a called oiilce where a register such as the one shown in Fig. 2 will be seized.

When a relay FDR is energized over the calling it causes the energization of a slow releasing relay AR. AR closes a circuit from ground at the called ofilce over the right-hand winding of relay JR, back contact and armature 2 of KR, the A wire. armature i and back contact of iCR. right-hand armature and front contact of AR, rectifier S winding of retardation coil RET, back contact and armature d of iCR, the ,3 wire, armature 3 and back contact of ICE, back contact and armature 2 of winding of JR to grounded battery. over its left-hand front contact and armature i and the B wire and energizes IHR over a circuit QR. The circuit remains in this condition until dialing commences. When the subscriber dials lDRwill fall ofi intermittently to close over its back contact an an ergizing circuit for a relay BR and a power magnet P. The latter controls the movement of brush ii. The relay BR is slightly slow releasing and does not fall oir between dial impulses. BR and P energize on the first pulse, whereupon the brush l0! moves from position 0 to position JR locks up 1 1. BR opens in its back contacts the trunk circuit so that the relay IDR will remain solely under the control of the calling subscriber. In its front contact and armature 8 BR energizes ICR which opens the normal trunk holding circuit traced through RET but not before a secondary holding circuit is closed over front contacts and armatures Z and ii of ICE. and front contact and armature 4 of BR whereby the incoming end of the trunk is not disturbed during dialing.

When the dial pulses cease lDR remains on its front contact long enough to allow BR to fall off and open the secondary trunk holding circuit. The quick releasing relay JR unlocks and closes its back contacts. The relay I CR at the calling omce and the relay II-IR at the called ofice are both slightly slow releasing so that a momentary circuit is established from ground over the front contact and armature 3 of IHR, back contact and armature ll of JR, back contact and armature 2 of KR. wire A, armature 2 and front contact of ICE, potentiometer mt, brush. illl, resistance RI, back contact and armature d of BR, front contact and armature E of iCR, B wire, ar-

IHR and the left-hand tact of IHR and conductor 8 to the grids of the ten valve circuits in the register. The Valve circuit corresponding to the potential applied .over brush IN to the B wire operates one of the gas valves and will cause the locking up of the proper storage relay XR, as previously described.

When ICE and BR release, the trunk circuit will again be closed overthe front contact of AR and the retardation coil RET causing the re-energization of JR over the armature 2 and back contact of ma.

The second, third and other digits are transmitted in the same manner.

The register is released by connecting conductor 8 to ground when all the digits have been recorded, as previously described. or an eleventh potential may be sent by the calling ofllce register and recorded on an eleventh valve circuit in the register of Fig. 2 to control the release.

When the called subscriber answers, the relay ISR in called ofllce operates and energizes KR which reverses the current flow in the trunk line and operates MR over rectifier S(-) to control metering in the usual manner.

It will be obvious to those skilled in the art that the invention may be modified in its electrical and mechanical details without departing from its spirit, and that it may be applied to controlling systems of many types and not only to those here specifically disclosed. y

In the claims presented hereinafter certain expressions are used to designate portions of this system which are described above in a general way. The expression "electronic switching 'device" is meant to designate the entire portion of the circuits shown in Fig. 2 which includes a plurality of pairs of triodes and of gas tubes associated therewith and of GVR relays. The expression potential comparing means refers more particularly to the individual devices within the electronic switching device each of which comprises a pair of triodes and a gas tube. The term electron discharge apparatus refers to the individual pairs of triodes. Its scope includes such a device as a double triode in a single glass envelope, a pair of individual triodes, or in fact. any multi-electrode discharge device which includes the essential elements necessary according to this invention (i. e. two controlled electron discharge paths) even though it contains additional non-essential electrodes. The term potential storing points designates the terminals in the outer bank of 'the E0 switch of Fig. 2 for the embodiment described herein. The controlling potentials" are the potentials selectedeither by the push button device shown in Fig. 1 (by being chosen from difierent points along a voltage divider) or selected by a mechanical switch, such as that shown in Fig. 3, which operates under the control of impulses from a dial such as that at the calling station I00 of Fig. 3.

What is claimed is:

1. A system as in claim 3, in which the plurality of sources of discrete controlling potentials comprises transformer-and-rectifier means adapted to receive an A. C. input and to translate it into at least one relatively large D. C. potential difierence, at least one voltage dividing means adapted to subdivide said relatively large D. C. potential difierence into a plurality of discrete D. C. potential differences, and gas tube voltage regulating means adapted to control the value of said relatively large D. C. potential difference;

2. A system as in claim 3, in which said means for transiently selecting one controlling potential at a time and applying it to the switching device comprises means including a plurality of keys and at least one voltage divider, for eflecting transient selective connections to discrete points on the voltage divider when keys are pressed.

3. A system for selectively connecting one or more sources of discrete marking potentials from a plurality thereof to one or more marking potentlal storing points in response to the transient selection of one or more controlling potentials from a plurality thereof, including pluralities of sources of discrete controlling potentials, comparing potentials, and marking potentials, one or more marking potential storing points, an electronic switching device for responding to a controlling potential of transient duration to connect an individual marking potential to a potential storing point in accordance therewith, means for transiently selecting one controlling potential at a time and applying it to the switching de'vice,

said device comprising a plurality of potential comparing means each one for comparing any controlling potential applied to the device with a 4 predetermined comparing potential to perform a switching operation when it is substantially equal thereto, each potential comparing means comprising an electron discharge apparatus whose electrodes include two cathodes, two control grids and' at least one anode and aflord two electron discharge paths, meansincluding a gas discharge tube having a control electrode and a main gap for performing the switching operation, means for applying to the control grid associated with one discharge path and to the cathode associated with the other all controlling potentials applied to the switching device, means for applying to the predetermined one of the comparing potentials, a common output path for the two electron discharge paths including an anode resistance and a source of anode potential connected in series, means for connecting said control' electrode to the end or said anode resistance iarthest from said source of anode potential, and a source of energizing potential for said main gap, the characteristics of the discharge apparatus and of the gas tube and the values of the anode resistance, the source of anode potential and the source of energizing potential being selected so that the the gas tube will ionize to perform the switching operation only when potentials of substantially the same value are applied to both grids and cathodes, and means including one or more sets of marking potential selecting relays, each set being individually associated with one storin point and responsive to the ionization of a particular gas tube to connect to said storing point one 01 the sources of marking potentials which corresponds to said particular tuber,

GERALD DEAKIN.

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